An on-ramp on San Marcos’ busy stretch of State Route 78 is set to close Friday night through Monday morning, officials said this week.

The eastbound 78 on-ramp at Barham Drive will be closed from 9 p.m. Friday through 5 a.m. Monday as crews reconstruct the ramp as part of a project to add new merging lanes nearby, according to the California Department of Transportation.

Detour signs will direct motorists around the closure, though Caltrans urged motorists to avoid area due to expected traffic delays. The agency said in a news release that heavy machinery will cause nighttime noise near the freeway exit.